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Up Topic Welding Industry / Technical Discussions / Welding TC Bolts
- - By jwright650 (*****) Date 02-24-2003 15:52
I have yet another job where the drawings are calling for the head of the 3/4"Diam. A325 TC bolt to be tack welded to the underside of a clip on some crippled beams for bleacher seating.(2 bolts per clip, 4 clips per beam)
How can you get around welding these bolts in?

There is another post on this subject but the list is getting rather lengthly.
John Wright
Parent - - By CHGuilford (****) Date 02-24-2003 17:29
You're right to be concerned. Short of inciting mutiny all you can do is to bring your concerns to the attention of the customer and/or your superiors. Likely your superiors will take the position that the drawing was approved that way (I'm assuming it was approved) so they may not want to question it. But at least you will have covered yourself.

As you know, welding of bolts happens a lot. It may well be that the design engineers considered the possibility of problems. As I mentioned before, there are some tests that can be done, however those don't take fatique loading and unusual conditions into account. So verifying that the people in authority are aware is the best you can do unless you have the authority to change the design.

Parent - By jwright650 (*****) Date 02-24-2003 17:39
I have written the AISC for alternatives or solutions to the situation. I'll post any responses I receive from them.

In the meantime I'd still like to hear of other alternatives to welding bolts.

DGXL and others have made me aware of the problems that could arise from this practice. Hopefully someone will have a cost effective solution.
I really would like to be able to present the engineers and detailers with something we can all "live" with. I shudder to think that something went through my shop and I "OK'd" a disaster waiting to happen.

John Wright
Parent - - By billvanderhoof (****) Date 02-25-2003 07:21
If the shank of the bolt is a bit larger than the threaded part undersized holes and press fit might work. If the bolt had a little knurl by the head (like an automotive lug bolt) that would be perfect but you can't have everything.
Parent - By jwright650 (*****) Date 02-25-2003 14:45
Yeah Bill, the problem is retaining the bolt until the connection is made, after the washer and nut are on it doesn't present a problem with access to the bolt head any longer(TC bolts). The wrench holds the bolt and turns the nut to proper tension before wringing off the spline so access to one side is all that is necessary after the washer and nut are installed. But before that, while you are swinging a heavy piece of iron in the air and trying to line up holes, that bolt that is just laying in the hole will most likely fall out the backside before you have a chance to get the washer and nut on. With hex headed bolts you then have a problem with holding the head while you are turning the nut for proper tension, provided you didn't knock the bolt out of the hole first.
John Wright
Parent - - By CHGuilford (****) Date 02-25-2003 14:25
There are alternatives, they just cost more to use. I like the ribbed shank idea. And in most cases, drilling & tapping can get around the problem. Trouble is, the labor, the thread quality and % of engagement, and the number of threads all play into it. These can be controlled, just not conveniently in a fab shop environment. You could even use a larger diameter bolt made from a weldable material. But you're going beyond the scope of AISC in any of these cases, hence the need for engineer's approval.
Hey, just a wild thought. What if you made your holes the bolt shank size or very slightly over, tapped the bolts in (without damaging threads), and Loctite them? You should be able to make them stay in as long as the ironworkers know what they are dealing with. For that matter, a piece of duct tape at the time of installation could work. No AISC violations there.
Chet Guilford
Parent - - By jwright650 (*****) Date 02-25-2003 14:50
All good thoughts there, Chet. The duct tape idea may just work. After the connection has been made unwrap the threads and carefully place the washer and nut on. Snug Tight and Torque to proper tension.
John Wright
Parent - - By jwright650 (*****) Date 02-25-2003 15:02
Just for thought,
The 3/4"Dia. A325 TC bolts has a shoulder that measures .746", so a hole .750" would be a press fit(.004" oversize). If you used a 3/4" drill bit instead of 13/16" punch (like we normaly do), that might work with some locktite for security.
John Wright
Parent - - By billvanderhoof (****) Date 02-26-2003 04:50
Thats what I had in mind above. Unfortunately .746 is .004 smaller than .750. Still if that is larger than the major diameter of the threads (even if the same size the damage to the threads would be slight) you could drill to 47/64 (.734) and ream with an adjustable reamer. Or perhaps have a bit ground down to drill the correct size. Those lug bolts with the knurl under the heads don't fall out. When you need one out it usually takes a punch and a good lick with a fair sized hammer. Of course if it was hanging on a crane 200 feet over the ocean and you didn't have a spare then a stiff breeze would blow it out of the hole. Murphy's law.

Come to think of it a truck lug bolt might be just the ticket, strong, available in the right size, knurled shank, even has government stamp (DOT). Unfortunately getting an engineer to sign off on it might be a problem.

Parent - - By jwright650 (*****) Date 02-26-2003 12:14
If the hole(.750") was any closer in size to the bolt shoulder(.746") you would have drive it in with dynamite. I think machinists call a .004" fit a "press fit", so maybe the locktite would help hold the bolts from being knocked out by the steel being erected.
John Wright
Parent - - By CHGuilford (****) Date 02-26-2003 14:18
Actually this is where I thought the duct tape could be used. After you install the bolts and Loctite 'em, and after painting if any, you could slap a piece over the head. It wouldn't be all that durable but it would provide some resistance to allow putting on the nut and washer, just in case the bolt got loose in shipping and handling. Naturally, tightening wouldn't be an issue with TC bolts as long as the nut is started on the threads.
Chet Guilford
Parent - By jwright650 (*****) Date 02-26-2003 21:37
Update from questions asked (AISC and Nucor Fasteners)

Here's what the AISC had to say....


Sorry for the delay in responding...I discussed your question with an ex-fabricator in the office, and I now have the following comments:
1. If possible, make the bolt accesible with access holes.
2. If possible, try using a bolt that is weldable (such as A307). This assumes that you don't have to pretension the bolts, as A307 can't be pretensioned.
3. There are U-shaped clips that are weldable that you could use to "clamp" the bolt head- and weld the clip.
4. If all else fails, you may have to weld the A325. This is not something that is recommended, as you may be damaging the heat-treatment of the bolt by welding to it.

Hope this helps.

Keith Mueller, Ph.D.

AISC Steel Solutions Center

And here is what Nucor Fasteners had to say....

Welding A325 TC or A325 hex bolts would never be our preference or recommendation. Proper tensioning could be compromised by a delayed fracture of the tack weld if the bolt bearing surface was not in full contact with the mating ply. Because there are so may variables, it is hard to say if the fastener would fail consistently due to the welding, but, it could. Technique and experience of the welder definitely could impact the results. Alternatives and solutions are more costly and that is why you hear mostly "thou shalt not" without solutions. The other reason is that most Fastener Engineers are not Structural Engineers and vice versa, therefore, familiarity with acceptable alternatives for problem connections are not common knowledge nor have they widespread publicaton or acceptance. Hopefully, tomorrow's Structural Engineers are learning some practical alternatives in their CE lab classes. The bottom line is that without review & consultation of a particular joint's problems it is hard to offer any constructive ideas/solutions. There may be some products on the market that could offer some assistance in temporary retention of the fastener in the hole until final assembly depending upon the weight of the fastener, but, it will be hard to universally apply them to all joints & assembly situations.

I know this hasn't helped much, but, I'll offer to discuss your assembly needs with you and offer any ideas I may have as your need arises as part of the service we offer at Nucor Fastener Division.

Roger Hamilton
Applications Specialist
Nucor Fastener Division

Thought I'd share the info that was received,
John Wright
Parent - - By billvanderhoof (****) Date 02-27-2003 05:26
Unless I'm reading something wrong here the bolt (.746) is smaller than the hole (.750) by .004. That's an easy slip fit. It doesn't get to be a press fit until the bolt is larger than the hole.
Parent - - By DGXL (***) Date 02-27-2003 06:16
Good reply to your own post, HIGH-5 yourself without having to see the chiropractor afterwards.

I tend to agree about welding HSB's not being a good idea. My opinion only. I mentioned I have various samples of A325's and 490's (or the A563 nut's) that have been 'modified', but were rejected. These include custom/proprietary configuration A325's. Lot's of ideas on this one.

I just hate humping a Skidmore around and prying the fastener out when your done.
Parent - - By jwright650 (*****) Date 02-27-2003 12:07
They ought to make those Skidmores motorized, and then they could carry themselves around. That little green box weighs a little over 100lbs!
John Wright
Parent - By jwright650 (*****) Date 02-27-2003 12:13
I really didn't think about it when I posted these questions on a "Welding" Forum when this is a "Non-Welding" question.
John Wright
Parent - - By jwright650 (*****) Date 02-27-2003 12:44
You're right, I've got it backwards as usual, I got my head on backwards too sometimes. Thanks for keeping after the idea and setting me straight.

see page 18 of this link describing a "Press fit"

John Wright
Parent - By jwright650 (*****) Date 03-03-2003 19:08
Here is more info that was received today from Bob at RCSC.

High strength bolts are quenched and tempered steels, and of a chemistry that is not easily weldable. You would likely have weld cracks if you tried to weld any high-strength bolt. There is no "spec" statement that says "thou shalt not", but any structural welding would have to be done with a qualified (tested) welding procedure under AWS D1.1, and I think you'd have a hard time getting a suitable PQR and WPS for high-strength bolting material.


Thanks to all who have replied and increased my knowledge on this subject,
John Wright
Up Topic Welding Industry / Technical Discussions / Welding TC Bolts

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